Electromagnetic Waves Excitation by Thin Impedance Vibrators and Narrow Slots in Electrodynamic Volumes

Linear vibrator and slot radiators, i.e., radiators of electric and magnetic type, respectively, are widely used as separate receiver and transmitter structures, elements of antenna systems, and antenna-feeder devices, including combined vibrator-slot structures. Widespread occurrence of such radiators is an objective prerequisite for theoretical analysis of their electrodynamic characteristics. During the last decades, researchers have published results which make it possible to create a modern theory of thin vibrator and narrow slot radiators. This theory combines the fundamental asymptotic methods for determining the single radiator characteristics, the hybrid analytic-numerical approaches, and the direct numerical techniques for electrodynamic analysis of such radiators. However, the electrodynamics of single linear electric and magnetic radiators is far from been completed. It may be explained by further development of modern antenna techniques and antenna-feeder devices, which can be characterized by such features as multielement structures, integration, and modification of structural units to minimize their mass and dimensions and to ensure electromagnetic compatibility of radio aids, application of metamaterials, formation of required spatial-energy, and spatial-polarization distributions of electromagnetic fields in various nondissipative and dissipative media. To solve these tasks, electric and magnetic radiators, based on various impedance structures with irregular geometric or electrophysical parameters and on combined vibrator-slot structures, should be created. This chapter presents the methodological basis for application of the generalized method of induced EMMF for the analysis of electrodynamic characteristics of the combined vibrator-slot structures. Characteristic feature of the generalization to a new class of approximating functions consists in using them as a function of the current distributions along the impedance vibrator and slot elements; these distributions are derived as the asymptotic solution of integral equations for the current (key problems) by the method of averaging. It should be noted that for simple structures similar to that considered in the model problem, the proposed approach yields an analytic solution of the electrodynamic problem. For more complex structures, the method may be used to design effective numerical-analytical algorithms for their analyses. The demonstrative simulation (the comparative analysis of all electrodynamic characteristics in the operating frequencies range) has confirmed the validity of the proposed generalized method of induced EMMF for analysis of vibrator-slot systems with rather arbitrary structure (within accepted assumptions). Here, as examples, some fragments of this comparative analysis were presented. This method retains all benefits of analytical methods as compared with direct numerical methods and allows to expand significantly the boundaries of numerical and analytical studies of practically important problems, concerning the application of single impedance vibrator, including irregular vibrator, the systems of such vibrators, and narrow slots

Multiband Asymmetric Biconical Dipole Antenna with Distributed Surface Impedance and Arbitrary Excitation

A numerical-analytical solution of a problem concerning the current distribution and input characteristics of asymmetric biconical dipole with distributed surface impedance and arbitrary excitation and derived in the thin-wire approximation. Solution correctness is confirmed by satisfactory agreement of numerical and experimental results from literary sources. Numerical results are given for the input characteristics of the dipole in the case of its asymmetric excitation by a point source

Multielement resonance diaphragms in microwave antenna-and-feeder devices

The resonance diaphragms are widely used in the antenna and microwave equipment as matching elements, filters, decoupling elements etc. As a rule the single-element resonance diaphragms or their serves along the direction of the wave propagation are used. Using the multielement resonance diaphragms may cause additional resonance couplings, changing the resonance frequency, matching the input and output of power electron microwave devices.This paper focuses on the theoretical description of the wave propagation or excitation of oscillations in the resonance system with a limited number of the resonance diaphragms

The point objective function for optimization of side lobes of linear antenna arrays

A new form of objective function is suggested for the problems of point optimization of complex radiation patterns of discrete antenna arrays. The function takes the properties of individual antenna radiators and the antenna array phase characteristic into account. Several examples of various antenna arrays help consider some properties of the point objective function and peculiarities of application of optimization of side lobes’ level using this function

The method of induced magnetomotive forces for cavity-backed slot radiators and coupling slots

The method of induced magnetomotive forces is used for solving the problem of magnetic current distribution in an antenna-waveguide structure of the “coupling slot in waveguide wall — rectangular resonator — radiating slot” type for the cases of infinite and semi-infinite rectangular waveguides. The numerical and experimental investigations of such systems are performed and the plotted electrodynamic characteristics are presented

Sidelobe reduction of two-dimensional waveguide-slot antenna arrays

The Galerkin's method is applied to the problem of electromagnetic wave radiation by two-dimensional waveguide-slot antenna arrays. The thickness of waveguide walls and interaction between slots were taken into account in numerical calculations

Asymptotic solution of integral equation into a problem of coupling between waveguides through narrow slots

On a basis of the asymptotic method of averaging the approximate analytical solution of the integral equation concerning a magnetic current in slot-hole coupling apertures of electrodynamic volumes was obtained. There are presented some expressions for currents and scattering characteristics of the transverse and longitudinal slots in the common broad and narrow walls of rectangular waveguides. The comparison with the results obtained by other methods is carried out

Energy characteristics of the slot system in the screen of coaxial line with controlled termination

The problem of excitation and radiation of the narrow circumferential or arc transverse slots array cut in the infinitely thin and perfectly conducting screen of a coaxial line with controlled termination has been solved with the magnetomotive forces method (MMF) in this paper. The frequency-energy characteristics of these systems are calculated taking into account the internal and external space interconnections between the radiators on conditions of arbitrary location of the slot elements and termination when internal and external spaces have been filled with the dielectric for any values of permittivity. The influence of location, value and phase of termination on the slot system radiation characteristics has been studied

Wave radiation of electrically long axial slot cut into the circular waveguide

The scattering problem of electrically long axial slot cut into side surface of the circular waveguide has been considered. Expressions of external self-admittance and transfer conductance were derived. The possibility of creation of a field distribution on the slot forms radiation pattern with low side lobes was shown

Closely spaced transverse slots in rectangular waveguide

The leaky-wave antennas in the form of closely spaced transverse slots cut in a broad wall of rectangular waveguide were investigated. The thickness of waveguide walls and interaction between slots were taken into account in numerical calculations